1% of wallets hold 68% of $133M in Polymarket midterm bets

An Anti‑Corruption Data Collective analysis found that on Polymarket Global, the top 1% of wallets accounted for 68% of $133 million placed on House and Senate contests through Aug. 10. Ten wallets alone produced 17% of trading volume and traded contracts relating to 426 of the 470 seats on the ballot.

The analysis compared 7,466 comparable congressional markets across Kalshi, Polymarket and Polymarket US with data current through Aug. 10. Traders had placed at least $133 million across those House and Senate markets by that date, up from $92.4 million in the entire 2024 congressional cycle. The count of comparable contracts rose from 464 in 2024 to 7,466 in 2026, including markets on general outcomes, primaries, endorsements, vote shares, turnout and candidate remarks.

Participation did not scale with the number of contracts. Across 39,820 Polymarket wallets, 87% of markets either had under $10,000 in volume or showed high volume concentrated in a small number of traders. Eighty percent of Polymarket’s congressional markets had fewer than 100 participating wallets. Only 10 markets had more than 1,000 wallets.

State-level activity was concentrated in a few contests. Contracts linked to the Texas, Maine and Michigan Senate races and Kentucky’s 4th Congressional District together made up 67% of state-level volume on Polymarket.

The analysis noted that contracts with low liquidity can move sharply when a single large order is placed. A price in a prediction market reflects the level at which traders are willing to buy and sell a contract at that moment, and a large trade can change that displayed probability even if public information about a race has not changed.

The ACDC projected that if 2026 repeats the late surge seen in 2024, total volume across the comparable markets could reach between $1.4 billion and $1.6 billion by Election Day. At the same point in 2024, about 8% of final volume had occurred, leaving the projection dependent on future trading patterns.

Regulators and exchanges have taken enforcement actions and opened investigations. The Commodity Futures Trading Commission has pursued individual cases involving misuse of confidential information and manipulation. Kalshi reported opening about 200 investigations in the prior year, and it said it froze accounts and imposed penalties in some instances.

Polymarket’s global venue uses pseudonymous wallets, which can make it difficult to identify the person or the information behind a trade without further investigative steps. The ACDC’s prior work found higher indicators of insider risk in markets settled on outcomes known to a small group, such as military or defense events, and lower indicators in public-outcome markets such as statewide elections.

ACDC extended that research across 78,496 longshot bets from 12,355 wallets and identified 152 highly specialized wallets active in military markets that had won more than $8 million. Those wallets met the study’s longshot criteria and showed higher win rates and returns compared with other trader categories. More than half of those wallets placed their first qualifying longshot within two days of account creation.

In remarks on Aug. 20, CFTC Chair Michael Selig outlined planned proposals to amend Parts 38 and 40 of the commission’s regulations. The proposed amendments would address event-contract listing rules, consumer protection, product governance, market design and incentive programs, and would define public-interest criteria for certain contract types.